gps!accuracyand!layarusability!testing! · your%ownreality%%%%%0%%% %%%%0%%%...

Your Own Reality -‐ http://stedelijk.medialab.hva.nl -‐ [email protected] -‐ @ml_sm

GPS accuracy and Layar usability testing Monday we went to the Museumplein to do a few very simple but necessary GPS accuracy tests. First and foremost, we’d like to make clear that this is not an extensive and thoroughly executed field research with a scientific foundation. We merely made some simple tests based on our practical experiences with the given techniques and infrastructure. We had an HTC Hero with Android 1.5 and an iPhone 3GS with firmware 3.1.3. There were certain points that we wanted to investigate. First, to what extent do the HTC Hero and iPhone differ from each other when it comes to GPS reception? Another point of attention was the reception of the points of interest within Layar. Finally there’s the accuracy of the coordinates within Google Maps and how this corresponds with the GPS software on the Hero and the iPhone. For this test we used the mobile applications GPSTest for the Android and TrackMyGPS for the iPhone. The first test: Google Maps

We chose three points near the Singelgrachtgebouw of the HvA and noted the coordinates given by Google Maps as shown on the picture to the left. Then we went outside and stood on those points with our smart phones. The results in the table above show that the differences between the coordinates are minimal. The Hero and the iPhone both approached the noted coordinates fairly accurately and do not differ much from one another. Some practical side notes: there was a loading time at each point of about 10 seconds.

Also, there was a delay with the reception. When you stood still, it took a couple of seconds to receive the information that you were not moving. A point that also needs to be taken into consideration is that we’ve used two different applications on

GPS ACCURACY TEST 1 HTC Hero iPhone 3GS Android 1.5 iPhone OS 3.13

Location LAT/LON Google Maps GPSTest 1.1.3 TrackMyGPS 1.0 1. Corner Singelgrachtgebouw LAT 52.360034 52.36006 52.359998 LON 4.909247 4.90932 4.909072 2. Corner bridge LAT 52.360478 52.36066 52.360436 LON 4.908821 4.90866 4.908850 3. Crosswalk Weesperplein LAT 52.361346 52.3612 52.361300 LON 4.908177 4.90755 4.907971


two different mobile platforms. One could question if the software simply grabs the coordinates given by the hardware or if there are differences between various mobile GPS-‐applications. Nevertheless, from this simple test can be concluded that the Google Maps-‐coordinates accurately correspond with the practical experience. The second test: GPS phone comparison

For the second test, we went to the Museumplein. We walked towards the Museumplein and stopped on seven random points along the way. This was a simple test to compare the GPS coordinates on the HTC Hero and the iPhone. As can be seen in the table above (and in test 1) both phones fairly accurately correspond with one another. Interesting side note: back at the MediaLAB the next day we entered the coordinates of point 5 of the Hero and of the iPhone into Google Maps, and it gave back two different points. The HTC Hero approached the result given back by Google Maps more accurately than the iPhone. It could be questioned why

the results differ when linked back to Google Maps even though test 1 shows that the phones do correspond with the online service. Why not so accurately the other way around?

GPS ACCURACY TEST 2 HTC Hero iPhone 3GS

Android 1.5 iPhone OS 3.1.3

Location LAT/LON GPSTest 1.1.3 TrackMyGPS 1.0

1 Jan Luijkenstraat / Honthorstraat LAT 52.35994 52.359899

LON 4.88137 4.881626

2 Jan Luijkenstraat / vd Veldestraat LAT 52.35941 52.359390

LON 4.87978 4.880011

3 vd Veldestr / Paulus Potterstraat LAT 52.35871 52.358721

LON 4.88019 4.880323

4 corner Van Gogh Museum LAT 52.35802 52.358128

LON 4.88096 4.880709

5 Ravensbrück monument LAT 52.35695 52.357027

LON 4.88219 4.882168

6 tramstop Museumplein LAT 52.35623 52.356327

LON 4.88079 4.881163

7 Albert Heijn Museumplein LAT 52.35713 52.357152

LON 4.87958 4.879624


The third test: Layar

The three POIs on the Museumplein.

The last test we did was a little more extensive than test 1 and test 2. This time we worked within Layar. We first stood still on the first point of interest (POI) that we placed on Museumplein. When we were standing exactly on the place where POI 1 was positioned, Layar gave as a result that we were standing 7 to 13 meters away from it. This discrepancy was formed on both the iPhone as the Hero. Then, standing on POI 1 and looking at POI 2 resulted in a given distance by Layar of 57 meters on the HTC Hero and 58 meters on the iPhone.

Looking from POI 1 to POI 2.

GPS ACCURACY TEST 3: LAYAR Point of Interest (POI) LAT LON 1 "Gewoon een punt" 52.357023 4.879978 2 "Mooi huisje" 52.356541 4.880373 3 "Blabla" 52.356709 4.88044 HTC Hero iPhone 3GS Location Estimate/Result Android 1.5 iPhone OS 3.1.3

On POI 1 0 8-‐13m 7-‐12m From POI 1 to POI 2 72 steps/73 steps 57m 58m On POI 2 0 5m 3m From POI 2 to POI 1 72 steps/73 steps 63m 61m


Michiel estimated that it would take 72 steps between both POIs. It took Erik 73 steps to walk from POI 1 to POI 2. When we were standing on POI 2 (looking at POI 2) we had a distance measured by Layar of 3 meters for the iPhone and a distance of 5 meters for the Hero:


Looking back from POI 2 to POI 1 through the augmented reality browser gave a measured distance of 63 meters for the Android and 61 meters for the iPhone. There are also some remarks that need to be made when it comes to the usability and experience of Layar. Due to real time movement and a certain amount of time to refresh, it takes about thirty seconds for Layar to position the POIs accurately in the browser. We also tested with video and audio and found out that, other than the iPhone, our HTC Hero could not play video (.mp4 and .3gp). Audio (.mp3) was no problem. We also did not get auto triggering to work, but that could be a scripting issue in the php-‐file. Last but not least, the POIs seem to be floating very much and it’s hard to walk around a 3D-‐object without it moving. It’s difficult to get 3D accurately fixed on location within Layar. The screen shots placed above give an impression of how the POIs look in Layar, but they are still static images. Below you can find three screen shots as the 3D POI 3 is approached. This POI was entered in a later stadium during the day to see how a smaller 3D-‐object looks like. In the left corner below of each still you can view the distance in meters. In map view:


In reality view:


In conclusion So, what conclusions can be connected to our test results? The first test shows that the coordinates given by Google Maps fairly accurately correspond with the coordinates on the iPhone and HTC Hero. It can also be said that the differences between both phones are minimal. This is also found in the results of the second test, although the discrepancy is rather strange to see when you link back the phone coordinates with Google Maps online. The last test we did gave us a very good insight on Layar and the practical experiences concerning the augmented reality browser. We noticed that, whilst standing on a point of interest, the browser shows that there’s an average distance measured of 5 or 6 to 10 meters. When it comes to usability, we can sum up a few things.

• It takes up to thirty seconds to get the POIs accurately positioned in the Layar browser.

• 3D objects seem to be floating and are difficult to strongly fix or accurately tie to location.

• Audio works on both the iPhone and the Hero, but the HTC has troubles with video.

• Smaller 3D-‐objects give a better visual experience and are better to fix to location than large 3D-‐objects.

We would again like to note that we did not use thorough measurement practices, but that we came to these conclusions merely based on practical experience and the information given back by Layar. For more visual impressions of our tests check our Flickr-‐set.

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